Flood Alleviation Sea Wall Reconstruction

Arup Rothwell were employed to provide Civil and Structural Engineering services to assist DfI with the reconstruction of the existing Sea Wall between the Gunsite Café and Perquage car park.

The existing sea wall was constructed by the German forces during the WWII occupation of the Island. The original wall was constructed with a rounded top approximately 8.4m AOD and was prone to overtopping by wave action, which was believed to be contributing to flooding in the Beaumont area.

In addition, the face of the wall had begun to degrade primarily due to a combination of abrasion of the face caused by wave action and corrosion of anti-tank reinforcement close to the face.

The project comprised the raising of the existing wall by 300mm, the addition of a recurve profile and concrete repairs.

The raising of the wall and new profile are intended to combat the flooding, with concrete repairs ensuring the longevity of the wall.

The existing top of the wall was removed via a combination of concrete sawing and splitting using pneumatic breakers. Compromised or degraded areas of concrete were then identified and broken out.

Cintec anchors were grouted into the existing wall at 0.5m centres to ensure a positive connection between the existing and proposed portions of the wall. These anchors were installed with threaded couplers so the wall could be raised further in the future — should this be necessary.

Reinforcement was fixed and the proposed recurved profile poured in in-situ reinforced concrete using bespoke steel shutters.

Finally, approximately 200m of the face of the existing wall was assessed with sprayed concrete repairs being undertaken in areas of severe degradation.

Project Scope
• Removal of top of existing sea wall.
• Installation of raised wall with recurve profile.
• Spray Concrete Repairs.

Arup Rothwell Scope
• Civil and Structural Design
• Site Supervision

Department for Infrastructure

Photo Credit
R.Fearnley & Geomarine Ltd